How do rubber (Hevea brasiliensis) plantations behave under seasonal water stress in northeastern Thailand and central Cambodia?

• Published in: Agricultural and forest meteorology 2015-11, Vol.213 (C), p.10-22
• Main Authors: Kumagai, Tomo’omi, Mudd, Ryan G., Giambelluca, Thomas W., Kobayashi, Nakako, Miyazawa, Yoshiyuki, Lim, Tiva Khan, Liu, Wen, Huang, Maoyi, Fox, Jefferson M., Ziegler, Alan D., Yin, Song, Mak, Sophea Veasna, Kasemsap, Poonpipope
• Format: Article
• Language: English
• Subjects: Cambodia; Control; Eddy covariance; Flux; Hevea brasiliensis; Plantations; Rubber; Seasons; Soil moisture; Stomatal control; Thailand; Transpiration; tropical deciduous forest; Tropical deciduous trees; Water balance; Water vapor flux
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2015.06.011

•Flux measurements were conducted at two rubber plantation sites in Southeast Asia.•Rubber trees at both sites maintain their water use even during the dry season.•Environmental and biological controls on rubber water use were investigated.•Thai rubber copes with water stress by using carried-over soil water from wet season.•Cambodian rubber utilizes deeper soil water and stricter stomatal regulation. Delineating the characteristics of biosphere-atmosphere exchange in rubber (Hevea brasiliensis Müll. Arg.) plantations, which are rapidly expanding throughout mainland Southeast Asia, is important to understanding the impacts of the land-use change on environmental processes. In attempt to shed new light on the impacts of conversion to rubber, we have conducted eddy flux measurements over a 3-year period in two rubber plantation sites: (1) Som Sanuk, located in northeastern Thailand; and (2) Cambodian Rubber Research Institute (CRRI), located in central Cambodia. Both sites have a distinct dry season. We used a combination of actual evapotranspiration (ET) flux measurements and an inverted version of a simple 2-layer ET model for estimating the mean canopy stomatal conductance (gs). The potential water balance (precipitation (P)−potential evaporation (ET_POT)) for each season (i.e., December–February: DJF, March–May: MAM, June–August: JJA, and September–November: SON) revealed when and how the water use is controlled. In the seasons when actual water balance (P−ET) was negative (DJF and MAM), the deficit was compensated with soil water from the previous season at depths of 0–2m (Thailand site) and 0–3m (Cambodia site). At both sites, the reference value of gs (gsref) and the sensitivity of gs to atmospheric demand (m) appeared to be less in DJF and MAM than each in the other two 3-month periods (seasons). On average, in a whole year, m/gsref was less in Thailand (